PWK Flat Slide Carbs (2014)

mschmitz57 said:

OK, time for an update (finally).
I wanted to post an status of my new PWK carbs. I finally got the bike out of the basement and into the garage for gas and oil.
The bike started on the first kick and and ran really well on the initial carb adjustments.
I did have to increase the idle speed a tad but that was it.
Before I started it I did have some overflowing problems with both carbs, and after removing one carb and dropping the float bowl
for inspection, the overflowing mysteriously stopped on both. Hmmm.
I wanted to seat the new rings so I was running it sort of hard, not caring too much about the idle settings, etc.
The first kick start surprised me because I had also freshened the top end this past winter. New rings, lapped the valves.
Also had Fred Eaton update my Power Arc ignition which cured my kickback problem. Many Thanks to Fred and Ella.
The bike restarted easily with 1 kick when hot. Looking forward to a long ride tomorrow.
I probably need to set the idle circuits a little more carefully but it runs strong and idles well.
I have a little bit of pippity-pop on deceleration but nothing objectionable. Maybe fatter idle jets in my future.
Also running new exhaust pipes so I may be leaking air.

I am running the Oval air filter pods from Mikes XS. They're quite a bit larger and look better.
So far so good.

Mark

http://s646.photobucket.com/user/mschmi ... t=3&page=1

Click to expand...

Mark, mysterious float bowl flooding, especially on modern carbs, can often simply be due to small particles of dirt in the fuel.

Amals seem unaffected by even large pieces of gravel and small mammals flowing through them! Modern carbs don't seem to be ale to handle dust particles!

Good quality in line filters are very much advised when fitting modern carbs to a 40 years old fuel tank.

The 2-in 2-out Pingel filter that Jim supplies in his plumbing kit is excellent. I fitted one to my Vincent. They are very expensive filters to buy, when you understand this, you understand that Jim's plumbing kit is very inexpensive.

Fast Eddie said:

mschmitz57 said:

OK, time for an update (finally).
I wanted to post an status of my new PWK carbs. I finally got the bike out of the basement and into the garage for gas and oil.
The bike started on the first kick and and ran really well on the initial carb adjustments.
I did have to increase the idle speed a tad but that was it.
Before I started it I did have some overflowing problems with both carbs, and after removing one carb and dropping the float bowl
for inspection, the overflowing mysteriously stopped on both. Hmmm.
I wanted to seat the new rings so I was running it sort of hard, not caring too much about the idle settings, etc.
The first kick start surprised me because I had also freshened the top end this past winter. New rings, lapped the valves.
Also had Fred Eaton update my Power Arc ignition which cured my kickback problem. Many Thanks to Fred and Ella.
The bike restarted easily with 1 kick when hot. Looking forward to a long ride tomorrow.
I probably need to set the idle circuits a little more carefully but it runs strong and idles well.
I have a little bit of pippity-pop on deceleration but nothing objectionable. Maybe fatter idle jets in my future.
Also running new exhaust pipes so I may be leaking air.

I am running the Oval air filter pods from Mikes XS. They're quite a bit larger and look better.
So far so good.

Mark

http://s646.photobucket.com/user/mschmi ... t=3&page=1

Click to expand...

Mark, mysterious float bowl flooding, especially on modern carbs, can often simply be due to small particles of dirt in the fuel.

Amals seem unaffected by even large pieces of gravel and small mammals flowing through them! Modern carbs don't seem to be ale to handle dust particles!

Good quality in line filters are very much advised when fitting modern carbs to a 40 years old fuel tank.

The 2-in 2-out Pingel filter that Jim supplies in his plumbing kit is excellent. I fitted one to my Vincent. They are very expensive filters to buy, when you understand this, you understand that Jim's plumbing kit is very inexpensive.

Click to expand...

You can dial out the pippity pop on de-accelleration by raising the needles a notch and making it richer. But if the popping quits when its warm then you may want to leave it because it is running lean and clean. Of course too much popping means its too lean. You balance it by lowering the needle until it pops a little when cold and then you know it is lean enough. If the needle is too high and rich the motor will load up when lugging and rolling on too much throttle at medium RPM at cruize or when pushing a headwind. The needle jet is the one variable that I have found hard to establish for the average customer. ,102 needle jets (no identifying mark) work good but usually require the needle to be lowered with the clip in the top notch - leaving no more adjustment. .101 needle jets (marked "1") allow you to run the needle clip 2nd from the top. .100 needle jets (marked "0") run the clip around the middle position or lower. The .100 " needle jets are just too lean for some customers and may need to be changed. Its easiest to jet to extremes (go full rich or full lean) when trying to figure this out.

But why should a Nort pop on de-acceleration when both the air and fuel are shut off anyway? Adding fuel makes the popping go away but its just wasting unburnt fuel. I think the little popping on de-acceleration is actually what you want. Then again a little popping is normal and you hear it happen with any race bike.

You will never have any problem with the machined surface inside the carb where the slides go. Those carbs will work great for many many years.

I have also seen some bowl flooding at first startup and then disappear never to come back after tapping on the bowl with a screwdriver handle and running the motor. I think it just takes a few minutes for the vibration to smooth off a sharp burr or two or for a little debris to clear out. But if flooding persists - shake the carb up and down and listen to hear if the float is free to rattle. I try to check this with every carb that goes out.

See my plug color below. I get the same plug color with;
.100 needle jets with the needles in the mid position,
or with .101 needle jets with the needle clip 2nd from top,
or with .102" needle jets with the needle clip in the top position.
Needle position and needle jet are something I need more feedback on.

The flooding was mysterious. I turned the fuel tap on and the dry bowls took a while to fill. Eventually the flowing stopped
after the bowls filled and I figured all was good. Then 10 seconds later both carbs burped some gas out the overflow tubes, then it stopped. This repeated every 10-15 seconds or so. At first I thought it might be air bubbles working their way out.
I removed the LH carb and removed the float bowl and everything looked fine. I verified that I could hear the floats rattling and that they were loose.

One observation I had was the float needle spring loaded shaft on the top of the needle. The spring seems really weak and the floats
tend to bottom out quite easily on the top of the float chamber. I wonder if this was causing a cyclical flooding.
I had installed a couple lengths of Tygon tubing on the side vents of the carbs as well, and I noticed the flooding stopped
after I removed these pieces of tubing. Not sure if the vent tubing could have been causing some odd pressure differential in the float chamber.

I've got around 100 miles on the bike now since the rebuild and it's running well. The popping seems to be minimal after the engine has warmed-up. I did re-adjust the idle and air screw setting. I think I'm running the air screws around 3/4 turn out so I may be looking at fatter idle jets. I did not start with new plugs. They started out sootier that they are now so I might raise the needles.
Mine are lighter in color that Jim's. I think I'd prefer a bit darker. I'll raise the needles as soon as I finish my beer.

I am pleased that my new exhaust pipes have not turned crazy colors. I used a product called "Blue Shield" which coats the inside of new pipes and I think It's working as advertised. I'm just starting to get a hint of straw color around the exhaust nuts. Very nice.

Here's what the plugs look like. A little darker in the picture.



I am running Jim's fuel filter setup as well so the fuel supply is squeaky clean.
Acceleration is really strong. No flat spots that I've noticed. Just gobs of lusty torquey acceleration in any gear.

Mark

mschmitz57 said:

... I've got around 100 miles on the bike now since the rebuild and it's running well. The popping seems to be minimal after the engine has warmed-up.
I did re-adjust the idle and air screw setting. I think I'm running the air screws around 3/4 turn out so I may be looking at fatter idle jets.
Here's what the plugs look like. I did not start with new plugs. They started out sootier that they are now so I might raise the needles.
Mine are lighter in color that Jim's. I think I'd prefer a bit darker. I'll raise the needles as soon as I finish my beer.
nd I think It's working as advertised. I'm just starting to get a hint of straw color around the exhaust nuts. Very nice.

I am running Jim's fuel filter setup as well so the fuel supply is squeaky clean.
Acceleration is really strong. No flat spots that I've noticed. Just gobs of lusty torquey acceleration in any gear.

Mark

Click to expand...

I wouldn't change the idle/pilot jets - you're good there. If you go to a fatter pilot jet then you will just have to open the mix screw more because it lets in air - not fuel. You may want to raise the needle clip a notch. Let us know what happens.

jseng1 said:

mschmitz57 said:

... I've got around 100 miles on the bike now since the rebuild and it's running well. The popping seems to be minimal after the engine has warmed-up.
I did re-adjust the idle and air screw setting. I think I'm running the air screws around 3/4 turn out so I may be looking at fatter idle jets.
Here's what the plugs look like. I did not start with new plugs. They started out sootier that they are now so I might raise the needles.
Mine are lighter in color that Jim's. I think I'd prefer a bit darker. I'll raise the needles as soon as I finish my beer.

I am running Jim's fuel filter setup as well so the fuel supply is squeaky clean.
Acceleration is really strong. No flat spots that I've noticed. Just gobs of lusty torquey acceleration in any gear.

Mark

Click to expand...

Click to expand...

I wouldn't change the idle/pilot jets - you're good there. If you go to a fatter pilot jet then you will just have to open the mix screw more because it lets in air - not fuel. You may want to raise the needle clip a notch. Let us know what happens.

OK, I raised the needle 1 notch (now in the middle notch) and it runs very well. Just the occasional pop during throttle-off downshift decelerating.
I think I may have a loose muffler to pipe connection leaking some air. Both air screws now set to 3/4 turn which seems to give the highest idle.
Cold startup is very easy. No flat spots or hesitation that I can detect. My PowerArc timing is spot-on.
Bike idles perfectly. Throttle response is instant. Acceleration is great. The bike runs so much better than with the single Mikuni I removed.

Overall I'm very happy with these.

Mark

You must have the .100 needle jets.

When your needle position is too rich - it will load up when lugging the motor at cruise in 4th gear (as in pushing a heavy headwind).

Greetings all. I know this is an old thread but I'll try for a response any way. The question I have for all of you who are using the PWK carbs is how on earth do you adjust the air screw on the right carb? It is so close to the left carb it's difficult to get to even with a home made right angle screw driver. These need to be manufactured left and right. What gives? Earl

Jim Schmidt soldered a bent wire onto the top of the screw so that a half turn of adjustment is available from the 1.5 out baseline. Works fine. All you need

Thank you. I 'll try it.

I would cut a shallow slot into the fuel mix adjustment screw head and then soft solder a piece of music wire that was short enough that it would turn all the way around without interference. Then I would push tiny clear vinal tubing over the wire so it extended slightly past the ends so you didn't poke yourself when adjusting.

These carbs will not work right until you get the idle right 1st. Below is the whole 9 yards on what I went through setting these carbs up for Nortons:



32mm PWK

Use only Special PWK needles #P11/32 available from JRC

start with130 main jet

Drill needle hole in slide to .120”

.101 needle jets 2nd needle position, or 102 needle jet with clip at top

#38 idle jet with idle mix screw approx 1/8 to 1 turn max. Change idle jets if necessary (usually smaller).

Bend brass tube inside float bowl to clear float, shake when assembled to make sure float is loose,

check idle bypass jet in carb throat is clear (.016”)

Stretch idle mix and idle speed spring for more tension

drill hole in side of main jet tower to 3/32 for more fuel flow

Use 8JS float needles (from JRC) or file the 4 corners off the float needle ridges near the rubber tip so it won’t hang up.

FLOAT LEVEL - Hold the carb upside down at a 45 deg angle so the pin in the float needle doesn’t compress. The float should be 3 to 4mm below the top of the central casting or lowest part of the aluminum carb body (not the main jet or the hex shaped main jet holder).

Use aircleaner K&N RC-2380

Hello,
There was a question about how the given profile could be machined for a better surface finish.
Well, the broaching process doesn't directly work with blind holes. But there are similar processes which do.
Also especially for powder metall parts there are calibration processes which give a near polished surface finish.
So, all it needs for the manufacturer (certainly only for the manufacturer!) is a bit of investment for this additional process.
The question still is, if it's really needed.
For all in this forum I wish a merry Christmas an a wonderful succesful new year with many miles on our NORTONs.
Best Regards
Klaus